High resolution solid-state NMR is widely used to determine the structure of biological macromolecules in solids. A variety of methods have been developed to measure both internuclear distances and torsion angles in molecules of interest. However, no experiments have been carried out to determine P-O-C torsion angles in nucleic acid backbones. We have developed a technique that can be applied to determine these angles. The method is based on measuring the correlation between "P chemical shift anisotropy andC5'-H, C3.-H dipolar couplings. Numerical simulations show strong dependence of the signal lineshapes on the P-O-C torsion angles. Barium diethyl phosphate is currently being used as a model compound, as its structure is similar to that of phosphate group in the nucleotide backbone. We aim to apply this technique to determine the structure of significant nucleic acids. SCEENTIFIC SUBPROJECT GRANT NUMBER: P41RR00995-23